Chitosan is a natural biopolymer with a high potential to serve as a carrier for drug and gene delivery. Several types of chitosan with and without modifications were reported for the delivery of gene therapeutic agents. Chitosan-based materials are biocompatible, condense effectively with oligonucleotides, are cheap, and can be transfected in several types of cells. The chemistry of chitosan, such as functional groups, enables structural modification to satisfy the requirements prior to use for the synthesis of an effective delivery system. This chapter introduces the applications of chitosan as a carrier for gene delivery. It covers the basic chemistry of chitosan and their modifications. Applications of chitosan as a carrier for gene delivery and the advantages and disadvantages of the chitosan-based carrier are summarized. This chapter is useful for researchers and scientists interested in the applications of chitosan as a carrier for gene-based therapeutic agents.